The present invention relates generally to surface processing including combination with bulk heat treatment, of alloys, and more particularly, to methods and processes for thermochemical treatment to reduce production time and cost, that minimize dimensional alteration, and the identification of alloys that possess properties and microstructures conducive to surface processing in such a way that the processed alloy possesses desirable surface and core properties that render it particularly effective in applications that demand superior properties such as power transmission components.
For iron-based metal alloy components, such as power transmission components, it is often desirable to form a hardened surface case around the core of the component to enhance component performance. The hardened surface case provides wear and corrosion resistance while the core provides toughness and impact resistance. In particular, a class of high-strength, high-toughness alloys is suitable for application of the thermochemical treatments.
There are various conventional methods for forming a hardened surface case on a power transmission component fabricated from a steel alloy, while retaining the original hardness, strength and toughness characteristics of the alloy. Conventional methods include carburizing via atmosphere (gas), liquid, pack, plasma or vacuum methods. Similarly, nitriding via gas, salt bath or plasma conventional methods may also be used to harden the surface. Alternatively, high current density ion implantation may be used to essentially eliminate subsequent dimensionalizing processes.
Different surface processing and bulk alloy heat treatment steps are often performed independently and in sequence which leads to extended processing times, costs and delivery.
Disadvantages with conventional surface processing and conventional bulk alloy heat treatments and properties include concerns with structure control, e.g. grain growth at high temperatures, quench cracking and softening in service because conventional alloy tempering temperatures are relatively low.
Thus, there remains a need for both reducing processing times, costs and delivery and also increasing the performance of surface hardened alloy products.
Accordingly, it is desirable to identify concurrent thermochemical process steps that, when applied to a class of high strength, high toughness alloys and products thereof, minimize the manufacturing cycle times, costs and delivery; while retaining the desired increase in performance capability. Products of the alloy class may be in multiple forms.